The present invention relates to printing devices. More particularly, the present invention relates to a media detector for and a method of differentiating between glossy-finish and matte-finish print media.
Printing devices, such as inkjet printers, use printing composition (e.g., ink or toner) to print text, graphics, images, etc. onto print media. The print media may be of any of a variety of different types. For example, the print media may include letter quality paper, transparencies, envelopes, photographic print stock, cloth, etc. These print media may be placed in one of two broad categories relating to the finish of the surface of the print medium. These categories are glossy-finish for things such as transparencies and photographic print stock and matte-finish for things such as letter quality paper and envelopes. A glossy-finish is specifically defined herein as a print media finish that provides a surface brightness or shine when illuminated by a light source. A matte-finish is specifically defined herein as a print media finish that lacks surface brightness or shine when illuminated by a light source. Glossy-finish and matte-finish print media each have various characteristics that ideally should be accounted for during printing, otherwise a less than optimal printed output may occur.
One way in which a printing device can be configured to a particular to print media is to have a user make manual adjustments to the printing device based upon these characteristics. One problem with this approach is that it requires user intervention which is undesirable. Another problem with this approach is that it requires a user to correctly identify and differentiate between glossy-finish and matte-finish print media which some users may be unable to do. A further problem with this approach is that a user may incorrectly manually configure the printing device so that optimal printing still does not occur in spite of user intervention.
A device and method that automatically differentiates between gloss-finish and matte-finish print media would be a welcome improvement. Accordingly, the present invention is directed to alleviating these above-described problems and achieving this end.
An embodiment of a media detector in accordance with the present invention for use in a printing device includes a source, a sensor, and a polarized filter. The source transmits an unpolarized first light signal and is positioned in the printing device so that the first light signal is transmitted toward a sheet of print media in the printing device at a first angle with respect to a normal to a surface of the sheet of print media. The sensor is positioned in the printing device to detect an intensity of a reflected light signal from the sheet of print media. The polarized filter is positioned between the sensor and the sheet of print media so that the intensity of the second light signal detected by the sensor is less for a polarized reflected light signal than for an unpolarized reflected light signal. Polarization of the second light signal is dependent upon the first angle.
The above-described media detector may be modified and include the following characteristics described below. The first angle may be selected such that the reflected light signal is polarized in a plane substantially orthogonal to a polarization of the polarized filter. The media detector may further include a second sensor and a second polarized filter. In this case, the second sensor is positioned in the printing device to detect the intensity of the reflected light signal from the sheet of print media. The second polarized filter is positioned between the second sensor and the sheet of print media, and oriented so that the polarization of the second polarized filter is substantially parallel to a polarization of the reflected light signal.
The reflected light signal may be polarized for a glossy-finish sheet of print media and unpolarized for a matte-finish sheet of print media. The media detector may be in a printing device. The first angle may be selected to be substantially equal to a Brewster's angle.
An alternative embodiment of a media detector in accordance with the present invention also includes a source, a sensor, and a polarized filter. In this embodiment, the source transmits an unpolarized first light signal in a first direction and the sensor is configured to detect an intensity of a reflected light signal having a second direction different than the first direction. The polarized filter is positioned between the sensor and a sheet of print media, and oriented so that the polarization of the polarized filter is substantially perpendicular to a polarization of the reflected light signal. Polarization of the reflected light signal is dependent upon the first direction of the first light signal.
The above-described alternative embodiment of the media detector may be modified and include the following characteristics described below. The media detector may further include a second sensor and second polarized filter. The second sensor is positioned in the printing device to detect the intensity of the reflected light signal from the sheet of print media. The second polarized filter is positioned between the second sensor and the sheet of print media, and oriented so that polarization of the second polarized filter is substantially parallel to the polarization of the reflected light signal.
The reflected light signal may be polarized for a glossy-finish sheet of print media and unpolarized for a matte-finish sheet of print media. The first direction may be selected to polarize the reflected light signal in a plane substantially orthogonal to a polarization plane of the polarized filter. The media detector may be in a printing device.
Another alternative embodiment of a media detector in accordance with the present invention for use in a printing device includes structure for producing a unpolarized first light signal and structure for sensing polarization of a reflected light signal from a sheet of print media in response to the first light signal so that the printing device can differentiate between a glossy-finish sheet of print media and a matte-finish sheet of print media to help optimize printing by the printing device. This alternative embodiment of a media detector for use in a printing device may include the following characteristics described below.
The reflected light signal may be polarized for glossy-finish print media and unpolarized for matte-finish print media.
The structure for sensing may include a sensor and polarized filter. In this case, the sensor is positioned in the printing device to detect an intensity of the reflected light signal from the sheet of print media. The polarized filter is positioned between the sensor and the sheet of print media so that the intensity of the reflected light signal detected by the sensor is less for a polarized reflected light signal than for an unpolarized reflected light signal. This embodiment of the media detector may also include a second sensor and a second polarized filter. In such cases, the second sensor is positioned in the printing device to detect the intensity of the reflected light signal from the sheet of print media. The second polarized filter is positioned between the second sensor and the sheet of print media, and oriented so that the polarization of the second polarized filter is substantially parallel to the polarization of the reflected light signal.
This alternative embodiment of a media detector may be in a printing device.
A method of differentiating between glossy-finish and matte-finish print media in accordance with the present invention for use in a printing device includes the step of transmitting an unpolarized first light signal toward a sheet of print media at a first angle with the respect to a normal to a surface of the sheet of print media. The method additionally includes the step of detecting an intensity of a reflected light signal from the sheet of print media. The method further includes the step of differentiating between a polarized reflected light signal and an unpolarized light signal to determine whether the sheet of print media has a glossy-finish or a matte-finish.
The above-described method may include the following additional steps described below. The method may include the additional step of selecting the first angle such that the reflected light signal is polarized in a plane substantially orthogonal to a plane including the normal. The method may include the step of selecting the first angle to be substantially equal to a Brewster's angle.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.